Continuous mud weight indicator



HQN. MARSH 2,311,312

CONTINUOUS MUD WEIGHT INDICATOR Feb. 16, 1943.

Filed Feb. 17, 1941 HALLAN N. MARSH lNVENTOl? FIG.3 LQMUJ TORNEYPatented Feb. 16, 1943 UNITED: STATES PATENT OFFICE CONTINUOUS MUDWEIGHT INDICATOR Hailan N. Marsh, Huntington Park, Calif., assignor toSocony-Vacuum Oil Company, Incorgorrakted, New York, N. Y., acorporation of New Application mime,- 17, 1941, Serial No; 379,168

1 Claim. (Cl. 265-44) The object of the invention is to provide a meansfor continuously ascertaining or recording the specific gravity of aflowing liquid, as for example the circulating fluid or drilling mu usedin drilling oil wells by the rotary method.

- In the drilling of rotary wells a thinly plastic mud is circulateddown the drill pipe and up through the casing surrounding it. for thepurpose of removing the drilllngs from the well as they are produced. Itis important to control the specific gravity of this mud, to adapt it toconditions encountered during the drilling or, the well, and to keep itsweight constant so long as these conditions do not change.

, Numerous devices have been proposed for obtaining a continuousindication or record of the mud weight, but all of them, so far as I amaware, areunreliable. I have discovered by experimenting with numerousdevices of this class that the inaccuracy is due in most cases to theaccumulation of suspensoids, usually solids, on the moving part of thedevice, 1. e.. the part which actuates the scale member. Inthe citedinstance of drilling mud this accumulation takes the form of a sheath ofheavy and partly solidified mud which contains less water and thereforeis heavier than the mud flowing through the apparatus. Where suchdevices are used for ascertaining or recording the weight of othersuspensions, as for example that of a stream of oily condensatecontaining suspended water particles, these particles attach themselvesto the moving part and increase its weight.

The device herein described is free from this source of inaccuracy forthe reason that. dynamic reaction of the moving stream being eliminated,it is possible so to increase the velocity of the flowing liquid as toprevent the segregation and shown, draws a stream of the fluid through atube i2 and discharges it through a tube l3 which is fixed in position.To the outlet end ll of the fixed tube is attached a floating tub l5which has a free discharge at its open end 16. Attachment is made bymeans of a section 11 of flexible tubing of such length and wallthickness as to interpose no appreciable resistance to a limitedvertical movement of the open end of tube I5.

This end'of tube I I is coupled to a weighing device or scale l8. Thisscale may be of any preferred type, with the reservation that it mustgive its full reading in response to only a minute vertical movement ofthe free end of tube l5. s The device suggested is. shown in section inFig.2, in which I8 is the enclosing case, i 9 is a drum shaft carryingthe indicating hand 20 in front of the calibrated face 2|, the shaftbeing supported on standards 22. A spiral spring 23 is attached a oneend to the drum and at the other to one of the standards. A silk cord orfine wire 24 is carried around the drum for at least one full turn andmade fast, the other end being attached to the free end of weighing tube15 as shown in 25Fig1 accumulation of the heavier constituents of thesuspension anywhere in the system.

The invention may best be understood with reference to the attacheddrawing illustrating preferred forms of the device in which:

Fig. 1, shows in elevation a simple form of the entire apparatus;

Fig. 2 is a cross-section through the scale elementI8ofFig.1;

Fig. 3 shows a fragment of a modified form of the device, in plan: and

Fig. 4 is a side elevation of the form of Fig. 3.

Referring first to Fig. l of the drawing. Ill represents any pipe orlaunder through which the fluid to be weighed is flowing under a lowpressure down to atmospheric. A small centrifugal pump I l, driven by amotor or other source of power not It is essential that, in its initialposition, the floating tube 15 be exactly aligned with the outlet end ofthe fixed discharge tube, and it is preferable that both be exactlyhorizontal. Also tube l5 should be so proportioned in relation to themovement of the travelling element of the scale that at no time will itdepart materially from its initial position of alignment with the tubeend I 4. This precaution will avoid any inaccuracy which would followfrom dynamic reaction, i. e., from the tendency of the tube to alignitself throughout as the fluid flows through it.

The floating tube should be polished inside and of a material offeringthe least possible selective action for the suspensoids. when these aresolid, as in the case of drilling mud, the tube may be of glass or of anoncorrosible metal. In the case of oils carrying suspended water, glassis undesirable on account of its water-wettability, In any case thevelocity through the floating or weighing tube must be sufficient tokeep its inner surface free from any deposit of suspended matter, and tokeep the tube filled with the liquid to be weighed.

A modified form of the device is illustrated in fragmentary form inFigs. 3 and 4. In this form the stationary end of weighing tube i5 isprovided with lateral branches 25-25 which are directly opposed and aresupported in minute trunnion boxes "-28. The branch tubes are suppliedfrom a common source such as a T 2'! to which they are. connected byhalt-loops of thin and flexible rubber tubing 28-28. In this form'thedynamic reaction is neutralized, since the tendency of the moving liquidfrom either of the branch tubes to move weighing tube IS in onedirection is exactly counterbalanced-by the tendency oi! liquid from theother branch to move the weighing tube in the opposite direction. Sincereaction is neutralized in any position which the weighing tube is freeto take, the weighing tube may travel through a wider angle than in theform first described without interfaring with the accuracy of the scalereadings. v

In either form of the invention the movement oi. the weighing tube l5may be caused to actuate the pen arm or scriber arm oi a recorder formaking a continuous record of the weight,

recorder arms.

and the indicating element" of the attached claim will be understood tocomprehend such I claim as my invention: A device for continuouslyweighing flowing liquids, comprising: a substantially horizontallydisposed tube supported at one end in a substantially fixed position onbearings and free to move at the other end; a weight indicatingelementoperatively connected with the free end of said tube; oppositelydisposed tubular branches flexibly communicating with said tubesubstantially at the points oof support of said tube on said bearings;and means for flowing said liquids through said branches and said tubetoward the free end of said tube at a velocity suificient to N. MARSH.

